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When backfilled soil causes strain, bulges in basement walls can result.

Perhaps the most catastrophic failures that we’ve witnessed in our inspection careers have been fully-inward-bulged (collapsed) basement foundation walls. Each failed wall (made entirely of hollow core concrete block) literally exploded into the basement followed by a river of mud or earthen landslide. If anyone had been sitting or standing near the wall at the time of failure, we doubt they would have survived. Fortunately, we’ve never heard of a serious injury or lost life, but we have witnessed the emotional grief/anguish that ensues once the homeowner finds out that their insurance policy will not cover the cost of cleanup or repair. Obviously, these costs can easily exceed tens of thousands of dollars.

When clay soils expansion occurs, foundation movements can result. It has been my experience that whenever an older home (say 15 to 20 years or more) that is constructed on highly plastic clay suddenly experiences cracking in brick or sheetrock, after many years of crack-free service, and there’s no other obvious answer to the problem, it’s probably related to drying shrinkage of underlying expansive clay subsoils. These subsoils probably remained wet each year, throughout the life of the home. Or, at least, the moisture change that did occur each year in the underlying massive clay soil was not sufficient to cause enough building distortion to, in turn, cause building material cracking. If the home suddenly develops cracks, however, there’s probably been some major change in the drainage conditions or landscape surrounding the home.

Foundation movements can result when clay soils shrinkage occurs.  A home-buyer transferring into the Huntsville metropolitan area once asked me, “What is the most common residential foundation problem that you see in your home inspection business?” I answered, “Differential foundation settlements (movements) due to expansive clay soils.” “Not so much expansion,” I explained, “but the opposite actually-or what we commonly call ‘shrinkage.’”